Optical scopes are used as an inspection tool to view inside an apparatus such as a turbomachine or engine. Optical scopes, such as borescopes, include a removable optical adapter tip at an end of the optical scope. The optical adapter is generally suited for various purposes, such as providing a discrete direction of view. The optical scope, including the optical adapter, is ingressed into the apparatus for viewing and assessing internal components.
In order to allow for periodic inspection of internal parts of the engine (e.g., blades, vanes, shrouds, disks, frames, etc.), borescope ports are typically provided in the engine casings and/or frames. Such ports allow optical borescope instruments to be inserted into the core engine to enable a visual inspection of the engine to be performed without requiring disassembly of the engine components. In an enclosed environment, such as inside a turbine engine, ambient light may be virtually eliminated. In such an environment, only artificial light provided by the borescope and associated lighting system may used to create an image.
Capturing details of the internal parts of the engine may be difficult due to the provided artificial light. For example, creating a clear borescope video of a turbine engine may be challenging due to the reflections from metal components and darker components of the engine. More specifically, reflections from metal components can create very bright parts of an image. On the other hand, other components within the engine may produce very dark parts of the image due to shadows, corrosion, or less reflective materials. Such contrasting bright and dark parts of an image may make it impossible to capture the details of both portions with a single image. For example, the bright parts of the image may be washed out, while the dark parts may be too dark to see. These issues may make perceiving defects or damage to engine components more difficult. The ratio of brightest to the darkest shades the system may capture simultaneously in a single image is generally known as the dynamic range.
Some inspection processes use methods such as high dynamic range (HDR) photography to capture images with both light and dark portions. In these methods, the camera exposure setting may be modulated with a constant light source. For example, multiple photos can be taken at different exposure levels and then combined with software to create an image with better contrast between the light and dark portions of the image. Such methods can create difficulties by requiring changes to the exposure and camera settings for every frame of video.
As such, there is a need for a method of capturing high dynamic range video using an optical scope without having to change camera settings, such as the exposure, between each frame.